Conventional drainage fields for land application of septic tank sewage effluent are constructed by digging trenches on land adjoining the septic tank. Filtering beds are created in these trenches by depositing a layer of filtering material in the bottom of the trenches. Conventional filtering material is rock, crushed stone gravel, sand, or a combination thereof. A network of perforated pipe is connected to the septic tank and laid in the trenches on top of the filter bed. Such systems normally operate by gravity flow, however, it is common practice to connect a pump to the septic tank to aid in moving the sewage effluent from the septic tank and through the drainage field, particularly where required by the lay of the land. The sewage effluent is distributed through the network of perforated pipes and trickles onto and through the filter bed, where its nutrient content is reduced by microbial action. After passing through the filtering material, the sewage effluent is absorbed by the soil surrounding and underlying the trench.
Standard practices, however, suffer from severe disadvantages. For example, conventional drainage fields for septic tanks require the transportation of heavy materials, such as the stone, rock gravel or sand required for installing filtration beds. In addition, conventional drainage fields generally operate for years, however, they must be dug up and replaced when they become clogged or otherwise stop functioning as designed. Replacement of the drainage field costs essentially as much as installing a completely new field, and perhaps more.